1. Field of the Invention
The present invention relates to an automotive push switch mainly used for lighting control of a stop lamp in operation of a brake pedal of an automobile.
2. Background Art
In recent years, pressing-type automotive push switches have been widely used for controlling a stop lamp, which is turned on when a brake pedal is depressed; turned off when released.
Such a conventional automotive push switch is described using FIGS. 8 through 11.
FIG. 8 is a perspective view of a conventional automotive push switch. FIG. 9 is a sectional view of the same. In FIGS. 8, 9, lower case 1 is open-topped, substantially boxy, and made of insulating resin. Actuator 2 is made of insulating resin. Lower case 1 has multiple fixed contacts 3 with their terminals 3A projecting from the bottom surface thereof, implanted therein. The top of actuator 2 has column-shaped operating shaft 2A extending upward.
Movable contact 4 is made of conductive metal. This movable contact 4 elastically contacts multiple fixed contacts 3 on their bottoms by means of contact spring 5 attached between movable contact 4 and the bottom surface of case 1 in a slightly compressed state. Then, multiple fixed contacts 3 are electrically connected to each other through movable contact 4 to form switch contact 6.
Return spring 7 is coiled. Upper case 8 covers the opening at the top of lower case 1. Return spring 7, attached between the undersurface of actuator 2 and the bottom surface of lower case 1 in a slightly compressed state, impresses thrusting force on actuator 2 upward.
Upper case 8 is provided with hollow pipe 8B projecting upward. Then, circular guide hole 8A vertically penetrates inside hollow pipe 8B. This guide hole 8A contains operating shaft 2A of actuator 2 inserted thereinto movably up and down. The top end of operating shaft 2A projects upward from hollow pipe 8B, and actuator 2 is housed in upper case 8 to compose automotive push switch 9. Here, a given gap is provided between the outer circumference of operating shaft 2A and guide hole 8A so that operating shaft 2A smoothly moves up and down.
FIG. 10 is an external view of a braking device using a conventional automotive push switch.
As shown in FIG. 10, conventional automotive push switch 9 is generally attached in front of brake pedal 10 of an automobile, and terminal 3A of fixed contact 3 has connector 11 connected to a stop lamp (not shown) attached thereto.
With brake pedal 10 not being depressed, arm 10A of brake pedal 10, biased counterclockwise, namely in the right direction, presses operating shaft 2A, resulting in actuator 2 moved downward in upper case 8. Multiple fixed contacts 3 separate from movable contact 4, causing fixed contacts 3 to be electrically disconnected from movable contact 4, and thus the stop lamp is off.
FIGS. 11A, 11B are sectional views of a conventional automotive push switch in operation.
In FIG. 11A, arm 10A obliquely touches the distal end of operating shaft 2A to press operating shaft 2A, and thus operating shaft 2A is pressed and retained with its distal end tilted upward and its outer circumference touching the surface of guide hole 8A.
Next, as shown in FIG. 10, with brake pedal 10 depressed, arm 10A rotates clockwise, namely in the left direction, centering on axis 10B, separating arm 10A from operating shaft 2A to remove the pressing force. Then, actuator 2 impressed by return spring 7 moves outward (refer to FIG. 11B). At this moment, as shown in FIG. 9, press contact spring 5 causes movable contact 4 to elastically contact multiple fixed contacts 3, which then connects fixed contacts 3 to each other to turn on the stop lamp.
As a prior art document related to the invention of this patent application, Japanese Patent Unexamined Publication No. 2004-47122 is known, for example.
In this way, with brake pedal 10 not being depressed, operating shaft 2A, the distal end of which is tilted obliquely upward, is biased downward in process of the rotation of arm 10A, owing to the tilt of arm 10A touching the distal end of operating shaft 2A and the thrusting force of return spring 7, according to arm 10A rotating in the left direction. However, operating shaft 2A swings momentarily between operating shaft 2A and guide hole 8A to hit the surface of guide hole 8A downward roughly vertically, thus causing a hitting sound due to the impactive force.